android實現簡單的畫畫板

畫畫板實現起來其實很簡單，我們只需要利用android給我們提供的Canvas類來操作就可以實現簡單的畫畫功能

直接看代碼，註釋都寫清楚了

public class MainActivity extends Activity {
	private ImageView iv;
	private Bitmap baseBitmap;
	private Canvas canvas;
	private Paint paint;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		this.iv = (ImageView) this.findViewById(R.id.iv);
		// 創建一張空白圖片
		baseBitmap = Bitmap.createBitmap(480, 640, Bitmap.Config.ARGB_8888);
		// 創建一張畫布
		canvas = new Canvas(baseBitmap);
		// 畫布背景爲灰色
		canvas.drawColor(Color.GRAY);
		// 創建畫筆
		paint = new Paint();
		// 畫筆顏色爲紅色
		paint.setColor(Color.RED);
		// 寬度5個像素
		paint.setStrokeWidth(5);
		// 先將灰色背景畫上
		canvas.drawBitmap(baseBitmap, new Matrix(), paint);
		iv.setImageBitmap(baseBitmap);
		
		iv.setOnTouchListener(new OnTouchListener() {
			int startX;
			int startY;

			@Override
			public boolean onTouch(View v, MotionEvent event) {
				switch (event.getAction()) {
				case MotionEvent.ACTION_DOWN:
					// 獲取手按下時的座標
					startX = (int) event.getX();
					startY = (int) event.getY();
					break;
				case MotionEvent.ACTION_MOVE:
					// 獲取手移動後的座標
					int stopX = (int) event.getX();
					int stopY = (int) event.getY();
					// 在開始和結束座標間畫一條線
					canvas.drawLine(startX, startY, stopX, stopY, paint);
					// 實時更新開始座標
					startX = (int) event.getX();
					startY = (int) event.getY();
					iv.setImageBitmap(baseBitmap);
					break;
				}
				return true;
			}
		});
	}

	public void save(View view) {
		try {
			File file = new File(Environment.getExternalStorageDirectory(),
					System.currentTimeMillis() + ".jpg");
			OutputStream stream = new FileOutputStream(file);
			baseBitmap.compress(CompressFormat.JPEG, 100, stream);
			stream.close();
			// 模擬一個廣播，通知系統sdcard被掛載
			Intent intent = new Intent();
			intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
			intent.setData(Uri.fromFile(Environment
					.getExternalStorageDirectory()));
			sendBroadcast(intent);

			Toast.makeText(this, "保存圖片成功", 0).show();
		} catch (Exception e) {
			Toast.makeText(this, "保存圖片失敗", 0).show();
			e.printStackTrace();
		}
	}

}

簡單的佈局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button1"
        android:onClick="save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:text="保存圖片" />

    <ImageView
        android:layout_above="@id/button1"
        android:id="@+id/iv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

</RelativeLayout>

再來個權限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

上兩張我畫的高端大氣上檔次的圖片。。。。